THE CHIMPANZEES AND ORANGS. 81 



Gorilla. The upper boundary of the nasal cavity, formed by the cribriform plate of the 

 aethmoid and the nasal bones, is on a level with the middle of the orbit in the Papuan, 

 but with the floor of the orbit in the Gorilla. The extent, therefore, of solid interorbital 

 median wall is much greater in the Gorilla, and forms a striking differential feature 

 with Man, as seen in the vertical section (Pis. XXVIII. and XXX.). 



Sinuses extend from the middle meatus upwards on each side this septum into the 

 interorbital space, as high as the base of the middle fourth of the superorbital ridge (/), 

 where they answer to the ' frontal sinuses ' of Man ; but, owing to the pecuUar deve- 

 lopment of that ridge in the Gorilla, they occupy no part that can properly be 

 called forehead in that animal. The superorbital ridge itself is chiefly composed 

 of solid bone with a small extent of minute cancellous structure in the middle of the 

 substance. 



The inner or vitreous table of the calvarium is better defined, where it is defined, in the 

 Gorilla than in Man, as is shown in the section (PL XXVIII.) for about an inch above 

 the foramen magnum, at the base of the lambdoidal crest, and along the posterior half 

 of the base of the sagittal crest ; elsewhere it blends with the outer table to form a dense 

 compact roof of bone. The whole of the enormous sagittal crest (n, s) is formed of 

 bony substance almost as compact. The basal half of the lambdoidal crest ( 3, Z) , exposed 

 by the section, is cancellous at its middle ; and the boundary line between this and the 

 sa"-ittal crest is well marked by the long venous canal continued downwards from the 

 foramen parietale (3). 



It is scarcely necessary to say that the parietal and lambdoidal cristae, which in the 

 Gorilla surpass in height those of all the Carnivora, do not exist, even rudimentally, in 

 any of the races of Mankind. The crucial ridge in Man is developed from a lower part 

 of the superoccipital than is the lambdoidal ridge of the Anthropoid apes. 



If we next proceed to compare the nasal chamber itself in the skulls of the Gorilla 

 and Papuan, we have first to notice the greater proportional length of that cavity in the 

 Gorilla, especially in the extent of its bony floor (20-22), but the turbinal plates have 

 not a corresponding antero-posterior extent. The premaxillary is relatively longer and 

 larger, and the part below the nostril, divided by the section at 22, PI. XXVIII., slopes 

 more forwards than in the Papuan. The answerable part (22, PI. XXX.), though 

 confluent with the maxillary in Man, is well defined by the incisive canal : this is 

 divided at its nasal end in the Gorilla, as in some Papuan and other Human skulls, 

 by the junction of a process of the premaxillary with the fore part of the nasal spine of 

 the maxillary (21). 



The remains of the premaxillary suture, which are obvious in the Gorilla for half an 

 inch upon the under surface of the palate, may be traced for an inch upwards and 

 backwards along the lateral wall of the incisive canal into the nasal cavity, where it is 

 lost, but appears again at the upper and lateral part near the nostril (PI. XXVIIJ. 22"), 



